<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>

  <style>
    .login-header {
      width: 100%;
      text-align: center;
      height: 30px;
      font-size: 24px;
      line-height: 30px;
    }

    ul,
    li,
    ol,
    dl,
    dt,
    dd,
    div,
    p,
    span,
    h1,
    h2,
    h3,
    h4,
    h5,
    h6,
    a {
      padding: 0px;
      margin: 0px;
    }

    .login {
      display: none;
      width: 512px;
      height: 280px;
      position: fixed;
      border: #ebebeb solid 1px;
      left: 50%;
      top: 50%;
      background: #ffffff;
      box-shadow: 0px 0px 20px #ddd;
      z-index: 9999;
      transform: translate(-50%, -50%);
    }

    .login-title {
      width: 100%;
      margin: 10px 0px 0px 0px;
      text-align: center;
      line-height: 40px;
      height: 40px;
      font-size: 18px;
      position: relative;
      cursor: move;
    }

    .login-input-content {
      margin-top: 20px;
    }

    .login-button {
      width: 50%;
      margin: 30px auto 0px auto;
      line-height: 40px;
      font-size: 14px;
      border: #ebebeb 1px solid;
      text-align: center;
    }

    .login-bg {
      display: none;
      width: 100%;
      height: 100%;
      position: fixed;
      top: 0px;
      left: 0px;
      background: rgba(0, 0, 0, 0.3);
    }

    a {
      text-decoration: none;
      color: #000000;
    }

    .login-button a {
      display: block;
    }

    .login-input input.list-input {
      float: left;
      line-height: 35px;
      height: 35px;
      width: 350px;
      border: #ebebeb 1px solid;
      text-indent: 5px;
    }

    .login-input {
      overflow: hidden;
      margin: 0px 0px 20px 0px;
    }

    .login-input label {
      float: left;
      width: 90px;
      padding-right: 10px;
      text-align: right;
      line-height: 35px;
      height: 35px;
      font-size: 14px;
    }

    .login-title span {
      position: absolute;
      font-size: 12px;
      right: -20px;
      top: -30px;
      background: #ffffff;
      border: #ebebeb solid 1px;
      width: 40px;
      height: 40px;
      border-radius: 20px;
    }
  </style>

  <body>
    <div class="login-header"><a id="link">点击，弹出登录框</a></div>

    <div id="login" class="login">
      <div id="title" class="login-title">
        登录会员
        <span><a id="closeBtn" class="close-login">关闭</a></span>
      </div>
      <div class="login-input-content">
        <div class="login-input">
          <label>用户名：</label>
          <input
            type="text"
            placeholder="请输入用户名"
            name="info[username]"
            id="username"
            class="list-input"
          />
        </div>
        <div class="login-input">
          <label>登录密码：</label>
          <input
            type="password"
            placeholder="请输入登录密码"
            name="info[password]"
            id="password"
            class="list-input"
          />
        </div>
      </div>
      <div id="loginBtn" class="login-button">
        <a id="login-button-submit">登录会员</a>
      </div>
    </div>
    <!-- 遮盖层 -->
    <div id="bg" class="login-bg"></div>
  </body>

  <script>
    let login = document.querySelector(".login");
    let mask = document.querySelector(".login-bg");
    let link = document.querySelector("#link");
    let closeBtn = document.querySelector("#closeBtn");

    let title = document.querySelector("#title");

    // 点击弹出层这个链接link让mask和login显示出来
    link.addEventListener("click", () => {
      mask.style.display = "block";
      login.style.display = "block";
    });
    // 点击 closeBtn 就隐藏 mask 和 login
    closeBtn.addEventListener("click", () => {
      mask.style.display = "none";
      login.style.display = "none";
    });

    // 开始拖拽
    title.addEventListener("mousedown", (event) => {
      // 鼠标移动的时候，把鼠标在页面中的坐标，减去 鼠标在盒子内的坐标就是模态框的left和top值
      let x = event.pageX - login.offsetLeft;
      let y = event.pageY - login.offsetTop;

      document.addEventListener("mousemove", move);
      function move(event) {
        login.style.left = event.pageX - x + "px";
        login.style.top = event.pageY - y + "px";
      }

      // 鼠标弹起，就让鼠标移动事件移除
      document.addEventListener("mouseup", () => {
        document.removeEventListener("mousemove", move);
      });
    });
  </script>
</html>
